The perfume and flavour industries mainly deal with ingredients which are known to be labile and volatile. The most volatile perfuming materials, also referred to as “top notes”, responsible for the first impact and freshness effect of a perfume, are the first to be lost during the manufacturing, storage and use of perfumes or perfumed consumer products. Therefore, the success of a perfume lies, not only in its olfactory identity, but also in its stability, as such as well as in consumer products.
Encapsulation techniques have been widely described in the prior art and used to a large extent, first of all as a means to improve the stability of volatile and labile ingredients such as fragrances or flavours, by protecting them from all kinds of possible aggressions or degradation processes such as oxidation.
Moreover, encapsulation is also a means to provide release of an active ingredient, which is spread out over a more or less extended period of time, instead of being instantaneous. In other words, encapsulation systems allow to slow the release of active ingredients, and therefore they may be suitable for an utilisation in applications wherein a controlled release is required, which is the case in many applications in the field of perfumery. In fact, since, as mentioned above, the most volatile fragrances, or “top notes” are responsible for the first impact in the consumer feeling, it is most of the time desirable that both less and more volatile fragrances are slowly released.
Finally, an encapsulated system can also constitute a means to improve the substantivity of molecules on a substrate, by providing a system capable of chemical or physical bonding with a particular surface or substrate.
Micro-encapsulation and inclusion complexes with specific materials such as cyclodextrins have been used in the prior art to decrease volatility, improve stability and provide slow-release properties of perfuming ingredients. However, when contacted with an aqueous medium, cyclodextrin based systems release the fragrance immediately, which limits their use as controlled release systems, in particular in applications involving an aqueous medium, such as in detergents.
Many other encapsulation techniques have been disclosed in the prior art and include for instance spray-drying, coacervation or yet extrusion. These techniques, while providing systems that stabilise and provide a certain controlled release of an active ingredient such as a perfume, do not however constitute systems capable of improving the sustained release of perfuming ingredients from substrates. Now, in particular in the field of functional perfumery, for applications such as detergents or fabric softeners, the substantivity of a perfume on a substrate such as a fabric constitutes an issue of paramount importance for the industry.
The absorption of perfume onto polymeric carrier materials, capable of improving the substantivity of perfume on surfaces, is also the subject of some disclosures from the prior art, in particular in the patent literature. More particularly the use of combined polymeric carriers has been described within the framework of perfume encapsulation, with the aim of improving the deposition of perfume on a substrate, in an application. As an example, U.S. Pat. No. 6,194,375 discloses organic polymer particles comprising perfume absorbed therein, and wherein a further polymer incorporating free hydroxyl groups is attached at the exterior of the particles. In a detergent application, the latter polymer serves to promote deposition of the particles from a wash or a rinse liquor during a washing cycle. Similarly, U.S. Pat. No. 6,329,057 describes polymeric particles comprising a hydrophobic organic matrix and, located at the exterior, free cationic groups and a further polymer which comprises free hydroxy groups. However, while providing an improvement of the deposition of perfume in application, by means of the use of a second polymer grafted at the surface of the particles, the latter systems do not allow simultaneously a controlled release of the perfume within a prolonged period of time.
EP 1146057 discloses polymeric nano-particles including olfactory molecules, which are described as producing the desired sustained and controlled release action in application. The described nano-particles are prepared by a semi-continuous batch polymerisation process consisting in continuously adding a liquid monomer component and a perfume to an aqueous solution of a first initiator comprising an emulsifier. Subsequently, a second and a third initiator are added to the reaction mixture. This process presents the drawback of mixing monomers with perfuming ingredients, possibly inducing contamination of the perfume with un-reacted monomers. Moreover, the perfume may react with free radicals during polymerisation and thus be subjected to degradation.
It can be concluded from the existing prior art that the industry still requires improvements in the field of polymeric encapsulation, and that, in particular, a delivery system providing at the same time a controlled release of an active ingredient there-encapsulated and an efficient deposition of said active ingredient on a substrate so as to obtain a sustained release from such a surface, is still needed. The present invention offers an efficient solution to the problems encountered in the prior art, by providing novel micro- or nano-particles, based on the use of a single polymer which has been chemically modified at its surface so as to be able to efficiently absorb a perfume. The particles or capsules of the invention protect the perfume during its use and storage, protect it from interactions with other constituents from a base when used to perfume a functional consumer product, and extend the release of the encapsulated perfume from a substrate. Moreover, the particles of the invention are prepared by a process which avoids any problem of contamination or degradation of the perfume unlike what was the case in the prior art.